Nowadays, communication access networks and, in particular, their Local Exchanges (sometimes called Central Offices) are adapted to provide a variety of subscriber lines, for example: basic analogue POTS (Plain Old Telephone Service) lines for delivering voice, various types of symmetric and asymmetric digital subscriber lines (DSL) being high-speed connection lines that use the same wires as regular telephone lines, so-called ISDN lines (Integrated Service Digital Network), which is a system of digital phone connections that allows voice and data to be transmitted simultaneously using end-to-end digital connectivity.
So-called broadband access networks are capable of delivering advanced voice, data and video services to end users (subscribers), by using enhanced DSL and ISDN solutions, and by interconnecting to IP, ATM and various wireless and cellular networks.
The conventional and worldwide accepted way of providing a private subscriber with telecommunication services usually means “tailoring” the access network infrastructure according to the end user's specific demand at the time of arranging the subscription. If the end user orders only a telephone voice service, he/she is given a conventional POTS line. In cases the end user wishes to get more advanced services at home, allowing him to use a digital telephone, a fax machine, a computer, the end user may receive a DSL line. For arranging local area networks for small offices or the like, and/or for easily using high rate data services, such as video and fast internet, the subscriber will be offered advanced DSL solutions, such as ADSL (Asynmmetric DSL), VDSL (Very high data rate DSL), SH-DSL (Single pair High bit rate DSL), ISDN, and/or other broadband telecommunication services.
So called Digital Subscriber Line Access Multiplexer (DSLAM) is a distribution unit located at the Local Exchange or at a street cabinet, which is positioned between the Local Exchange and the subscribers, comprises a plurality of different “line cards” which suit to different types of services available from the Local Exchange and ordered by the subscribers. For example, a DSLAM may include, in various combinations, a number of POTS (voice only) line cards for voice only subscribers, a number of ADSL cards for residential asymmetric services, a number of SDSL cards with a single or multiple pairs for symmetric services, a number of VDSL cards for symmetric business services or asymmetric high speed residential services, a number of combined POTS and DSL cards (so-called Integrated Voice-Data “IVD” cards), etc.
Each subscriber, when first connected to the Local Exchange, obtains the service according to the personal demand. In most cases, connecting a new subscriber to the Local Exchange requires rewiring the DSLAM at the Local Exchange. In case the DSLAM is located in a street cabinet, connecting a new subscriber to the Local Exchange will mean a special visit of a technician to the street cabinet.
Once the subscriber decides to upgrade or downgrade the communication services in the premises, a technician may need to rewire the DSLAM at the Local Exchange or the street cabinet and add or replace the installed line cards in the DSLAM, if the specific requested service penetration exceeds preliminary expectations with respect to the mixture of line cards in the DSLAM.
U.S. Pat. No. 5,903,372 describes an apparatus for remote addition of video services to subscriber, which comprises an optical network unit (ONU) connected by an optical fiber to a remote terminal such as CO. The ONU is intended for installation in a neighborhood of primary subscribers (those which require only POTS lines) and secondary subscribers (those who order video services). The ONU comprises POTS cards, switchable video cards, dedicated video cards (i.e., combined with POTS), and hard-wired video cards. The subscribers' requirements may change from time to time. The ONU includes a switch matrix card that, being remotely controlled from the CO, is capable of connecting the primary and the secondary subscribers to the service cards and/or their combinations, which respectively suit to the specific current requirements of the subscribers.
Both the installation and maintenance of such an ONU, if installed in a street cabinet, seems to be quite expensive. Furthermore, the number of cards to be installed of each of the types should be decided at the time of installing such ONU, a fact that adds to the problems associated with this solution.
In any of the described cases, determining the optimal ratio between the broadband services and narrowband services in the access networks (i.e., and therefore the mixture of line cards in each distribution unit) is always a multi-parameter task, since it should take into account the present demand, the technological and sociological trends, as well as various economical factors.